A pit-mounted dockboard is a common type which is mounted in a pit or depression in the loading dock. The dockboard includes a ramp which is pivoted at its rear edge to the frame or supporting structure, and a lip is hinged to the forward edge of the ramp and is movable between a downwardly hanging pendant position and an extended position where it forms an extension to the ramp. When in use, the extended lip will engage the bed of a carrier or truck positioned in front of the dock to bridge the gap between the dock and the truck. After the loading operation is completed and the truck pulls away from the dock, the lip will pivot downwardly to the pendant position.
In a conventional hydraulically operated dockboard, a hydraulic cylinder unit interconnects the frame and the ramp. By operating the cylinder unit to extend the piston rod or ram, the ramp will be pivoted upwardly to an inclined position. Hydraulic dockboards also include a mechanism for lifting the lip from the downwardly hanging pendant position to the extended position as the ramp is elevated. In some types of hydraulic dockboards, a mechanical linkage is used to raise the lip, while in other hydraulic dockboards, a separate hydraulic cylinder unit is employed. In the latter situation, where a separate lip lifting cylinder is utilized, the lip lifting cylinder can be operated through separate manual controls, or in other cases, the lip lifting cylinder is interlocked with operation of the main cylinder so that hydraulic fluid will be supplied to the lip lifting cylinder from the hydraulic system when the ramp is elevated to a predetermined position.